1. Field of the Invention
The present invention relates to method and an apparatus for automatic cooking in a microwave oven which are capable of executing automatic cooking in an optimal state by detecting an outflow air temperature and a weight of food to be cooked and calculating a cooking time using detected signals relating to the outflow air temperature and the weight of food with fuzzy control.
2. Description of the Prior Arts
Various types of microwave cooking methods and apparati are well known in the art. One conventional microwave oven is illustrated in FIG. 1. As shown in FIG. 1, the conventional microwave oven comprises a microcomputer 1 for controlling the operation of the whole system, a driving section 2 for supplying magnetron driving power, fan motor driving power, and turntable motor driving power under control of the microcomputer 1, a magnetron 3 for generating a microwave by being driven by the magnetron driving power from the driving section 2, a heating chamber 7 for heating the food positioned on a turntable 8 with the microwave generated at the magnetron 3, a cooling fan motor 5 which is actuated by the fan motor driving power from the driving section 2, a cooling fan 6 for blowing air in the heating chamber 7 through an air inlet 10 and cooling the magnetron 3 upon activation by the cooling fan motor 5, a turntable motor 9 for rotating the turntable 8 by being actuated by the turntable motor driving power from the driving section 2, and a weight sensing section 4, disposed below the heating chamber 7, for detecting the weight of the food and applying the detected weight signal to the microcomputer 1 as an electrical signal.
With reference to FIG. 2 the operation of the conventional microwave oven is described below.
Upon pressing a button for cooking in a state that the food to be cooked is positioned on the turntable 8 within the heating chamber 7, the microcomputer 1 executes an initial heating operation.
That is, the cooling fan 6 is actuated for a predetermined time by the driving section 2 to blow air into the heating chamber 7 so that the air temperature within the heating chamber 7 is uniform.
When the predetermined time has elapsed, the microcomputer 1 actuates the turntable motor 9 to rotate the turntable 8 on which the food to be cooked is positioned, and the magnetron 3 is driven by the driving section 2 to heat the food within the heating chamber 7. On the other hand, the weight sensing section 4 disposed below the heating chamber 7 detects the weight of food and converts the detected weight signal into an electrical signal and applies it to the microcomputer 1. As a result, the microcomputer 1 stores the weight signal W1 therein and multiplies the weight signal W1 by a predetermined constant C responsive to the kinds of food, thereby calculating a first stage heating time T1, as shown in FIG. 2.
The magnetron 3 is strongly actuated for the first stage heating time T1 calculated as above, and thus the food within the heating chamber 7 is heated as time elapses.
Thereafter, upon completion of the first stage heating time T1, the microcomputer 1 executes a second stage heating operation by calculating a second stage heating time KT1 by multiplying the first stage heating time T1 by a predetermined constant K and weakly actuates the magnetron 3 for the calculated second stage heating time KT1 to continuously heat the food.
Thereafter, when the second stage heating time KT1 elapses, that is, when the whole cooking time T2 has elapsed, the magnetron 1 stops the driving of the magnetron 3, the cooling fan 6 and the turntable motor 9 and finishes the cooking operation.
In such a conventional microwave oven, the first stage heating time is calculated by multiplying the weight of food detected at the weight sensing section by a predetermined constant in accordance with the kinds of food and the first stage heating operation is executed for the first stage heating time, but it executes the cooking operation indiscriminately with respect to the food of same kind and weight irrespective of the condition and shape of the food, resulting in the over heating or incomplete heating of the food.
Furthermore, since the first stage heating is executed for the first stage heating time which is calculated in response to the weight signal, the reliability of cooking becomes lower in the region where the voltage level is not irregular, and in case that an error occurs in the weight sensing signal of food detected at the weight sensing section, the cooking time may also involve an error, thereby causing the cooking condition to be poor.